Recommend me a Trail tyre...

I've been running Nobby Nics front and rear for the last 7/8 months and up until recently been more than happy with them. During my last 2 visits to Cannock on the dog i've noticed that the front seems to feel more and more skittish and doesn't give much grip. I'm running low pressures as they are tubeless on Stans rims.
Not usre wheteher the trails have been eaten up a bit recently but the top surface felt quite loose??
I'm off to Coed y Brenin in a few weeks time and should imagine the traila are packed quite similar to Cannock.

Don't need UST. Any tyre will do as they'll be going on Stans Arch rims?
Just a thought... Could this lack of traction have anything to do with going from a DT Sqiss 5.1 rim (which is 28mm wide) to the Stan's Arch (24.3mm)?